This program covers the long-standing development of laser microsurgical techniques; its primary focus for the last 3 years has been in cardiological applications, in particular laser angioplasty. Excimer lasers coupled to fused silica fibers were examined, as well as more conventional sources (pulsed carbon dioxide and Nd:YAG lasers and continuous-wave argon and dye lasers). New IR laser sources have been developed (in conjunction with Naval Research Lab and Quantronix Corp.) which utilize strong water absorption and can be transmitted through low-loss, cladded optical fibers. They include the first use of the Erbium:YAG laser @2.94um through zirconium fluoride optical fibers and the Thulium:YAG (Cr-doped) @ 1.96-2.Olum through low-OH silica optical fibers. Our collaborations with the NRL and various industry groups have led to a variety of prototype laser microsurgical systems for angioplasty studies. The collaboration with MCM Labs has led to clinical trials of peripheral and, more recently, coronary laser angioplasty using a pulsed dye laser with computer-controlled fluorescence guidance. Application of our infrared lasers (particularly the Tm:YAG and silica optical fibers) to laser angioplasty systems is proceeding with parallel development of a clinical infrared version of the fluorescence guidance system and a new intravascular ultrasound/laser catheter.